Control for pancake-type variometers



March 15, 1927. 1,621,018

V.'D. LANDON CONTROL FOR PANCAKE TYPE VARIOMETERS Filed Oct.15, 1923 WITNESSES: INVENTOR ZR '3Q9 M zsv g Verna/7 0. Landm BY W 7 ATTORNEY Patented Mar. 15, 1927.

UNITED STATES PATENT ()FFIQE.

VERNON I). LANDON, OF EAST PITTSBURGH, :EENHSYLVANIA, ASSIGNOR 'IO WESTING- HOUSE ELECTRIC MANUFACTURER VANIA.

'0'. COMPANY, A CORPORATION OF PENNSYL- CONTROL FOE I.!.I TCAKE-TYPE VARIOI'JIETERS.

Application filed October 15, 1923.

This invention relates to means for ad justing the constants of a radio circuit and it is particularly applicable to adjusting the inductance in the tickler circuit but it can be used in connection with any circuit in which the inductance is to be adjusted and may be substituted for any of the usual variometers.

It is an object of this invention to provide a mounting for coils of the pancake type by means of which the mutual inductance between them may be readily varied.

It is a further object of this invention to provide a structure that may, by relatively easy changes in the position and size of the parts, he designed to produce predetermined results.

More specifically stated, this invention enables the designer, without altering the size or individual inductance of the coils. to provide for a maximum mutual inductance in one position, a minimum mutual inductance in another position, and afull 180 degree movement of the dial to change from one of these positions to the other. Within ordinary limits, the limiting values may be wholly arbitrary and yet the dial movement kept a full half-turn.

Because the linear distance between the two positions of the center of the movable coil determines the change in the inductance, it has heretofore been considered necessary to move it through a straight line. The present invention makes use of the fact that a curved motion is equally available.

Other objects of the invention and details of the construction will be apparent from the following description and the accompanying drawings in which Figure 1 is a front view of the device with a portion of the panel broken away.

Fig. 2 is a top plan view, certain parts being shown in section.

The apparatus includes a stationary coil 1 and a movable coil 2. Each of these coils is wound in a way that will minimize its capacity. For example, the coil 1 is wound upon a disc 3 which is provided with a plurality of radial slots. The wire of the coil is passed through each slot so that the lengths of wire from one slot to the next lie alternately on opposite faces of the disc. The wire is wound into a flat spiral, the sev- Selial No. 668,548.

eral turns being separated from one another by a distance sufficient to insure that the distributed capacity shall be small. Any suitable arrangement for holding the turns in place may be used, such as spacers inserted in the slots or notches in the edges of the slots.

The disc 3 is held in place by means of a pair of brackets 4 and 5 which also serve as binding posts to which the ends of the winding are attached. The brackets 4t and 5 are secured to a shelf 6. which may support the panel 7 or may be supported thereby.

The movable coil 2 is wound upon a similar disc 8, the same precautions for minimizingdistributed capacity being used. The The disc 8 is secured to a head 9 upon the end of an arm 11, which is keyed to a shaft 12. One end of this shaft is mounted in a panel 7, as shown at 13 in Figure 2. The other end is mounted in a bearing 14 at the upper end of a post 15, which forms the upright part of a bracket 16 secured to the shelf 6. The bearings 13 and 14- are carefully aligned so that the motion of the coil 2 is in a plane parallel to the coil 1. Also, the bearings lit the shaft closely so that no material departure from this plane can occur. Preferably, the bearings fit with sufficient tightness to afford enough friction to hold the shaft 12, and so hold the coil 2. in any selected position. If desired, the friction may be increased by tightening the screw at the rear end of the shaft, so that the washer 17 bears with a greater pressure against the bearing 14. This also causes increased friction between the shoulder 18 at the front end of the shaft 12 and the front surface of the panel.

The enlargement made at the front end of the shaft to provide this shoulder also carries a dial 19 and a milled head 20. The dial is so positioned on the enlargement that a small clearance is left between the beveled edge of the dial and the surface of the panel. This prevents the dial from defacing the panel. The dial may be a complete circle or only a semi-circle, as desired. Graduations. extending over a semi-circle only, are sutficient, but greater convenience is secured if they extend over a complete circumference. The panel carries a reference mark 21 for convenience in noting the position of the dial.

Figure 1 illustrates the movable coil in the position in which the mutual inductance between it and the coil 1 is a maximum, the dial be rotated 180 degrees, the coil will assume the dotted-line position 2, in which the inductance is a minimum, or even negative. If the dimensions of the several parts of the device are as illustrated in Figure 1, the mutual inductance of the coils 1 and 2, When the coil 2 is in the dotted-line position, will be opposite in sign to the mutual inductance When the coil 2 is in a full-line po- .sition. There will, therefore, be intermebe so designed that the movable coil never reaches this position. lVhatever position is selected to determine the maximum inductance, the position for minimum inductance will be at adefinite distance from it, because the mutual inductance depends on the distance apart of the axes of the coils. Having determined the two extreme positions of the movable coil, the apparatus is designed by locating the shaft 12 half-way between the two limiting positions of the center of the coil 2 and on the line joining these positions. This will give 180 degrees change in the reading of the dial for the maximum change in the inductance. If it is desired to use a dial having less than 180 degrees motion to correspond to the maxi mum change of inductance, the shaft 12 will be positioned at one side of the line joining the two positions of the center or the coil 2, and the arm 11 will be correspondingly longer.

For the sake of clearness in the illustration, the coil 2 has been shown as having a smaller diameter than the coil 1 but it will be evident that the two diameters may have any desired relation. If the coil 2 is larger than the coil 1, the brackets 4 and 5 must be high enough to permit the center of the coil 2 to descend to the center of the coil 1.

It will be obvious to those Skilled in the art that numerous details of the structure may be varied without departing from the spirit of this invention. 1 do not intend therefore, that it shall be limited except as necessitated by the prior art and indicated in claims.

1 claim:

1. In a device of the class described, a flat coil, stationary means for mounting said coil, a shaftrotatably mounted at right angles to the plane of said coil, an arm carried by said sha 't and a second fiat coil at the end of said arm parallel to the first named coil, whereby rotation of the shaft will move the movable coil in a plane parallel to the stationary coil and thereby alter the mutual inductance of said coils, said stationary coil being beyond the end of said shaft whereby said stationary mounting means may be located to provide any desired change of degree of overlapping of said coils in half a revolution of said shaft.

2. In a device of the class described, a flat coil, stationary means for mounting said coil, a shaft rotatably mounted at right angles to the plane of said coil, an arm carried by said shaft, a secondflat coil secured at the enn of said arm parallel to the first named coil, whereby rotation of the shaft will move the movable coil in a plane parallel to the stationary coil and thereby alter the mutual inductance of said coils, and a graduated dial secured to said shaft to rotate therewith, said stationary coil being on the side of said arm opposite said dial and beyond the end of said shaft.

In a variable inductance, a pair of flat coils, means for moving one of said coils rel ative to the other, said means including a shaft midway between the two extreme positions of the movable coil, said shaft being whplly outside the plane of the stationary con.

In testimony whereof, I have. hereunto subscribed my name this 9th day of October, 1923.

VERNON D. LANDON. 

